Hair dye compositions are classified depending upon the types of dyes to be used or the presence or absence of a melanin bleaching action. Typical examples of the hair dye compositions include a two-agent type oxidative hair dye composition consisting of a first agent containing an alkali agent, an oxidation dye and an optional direct dye such as a nitro dye and a second agent containing an oxidizing agent; and one-agent type non-oxidative hair dye composition containing a pH adjuster (acid or alkali) and at least one of direct dye such as an acid dye, a basic dye and a nitro dye.
As the direct dye to be used in these hair dye compositions, a dissociative azo dye is known which contains a dissociative proton in a molecule and displays a color by dissociation of the proton (for example, Patent Document 1).
[Patent Document 1] JP-A-2003-342139